Handy printer system

ABSTRACT

A system and a method of printing an image represented by a frame of image data utilize a hand-held printer having optical sensors for tracking positions of the hand-held printer relative to the surface of a print medium during a printing process. The change in position of the hand-held printer during the printing process is monitored in real time using navigation information generated by the optical sensors. Each optical sensor contains an array of optoelectronic elements to capture images of the surface of a print medium at fixed time intervals. Preferably, the optical sensors can detect slight pattern variations on the print medium, such as paper fibers or illumination patterns formed by highly reflective surface features and shadowed areas between raised surface features. These features can then be used as references for determining the position and the relative movement of the hand-held printer. During the printing process, the printed portions of the image can also be used as reference positions by the hand-held printer. In the preferred embodiment, the hand-held printer contains a navigation processor and a printer driver. Using the printer driver, the navigation processor drives the hand-held printer to print segments of the image onto a print medium as the hand-held printer travels across the print medium during a printing process. Each segment of the image is printed onto a particular location on the print medium to form a composite of the image.

TECHNICAL FIELD

The invention relates generally to printing methods and systems and moreparticularly to approaches for determining a sequence for depositing inkonto a print medium.

BACKGROUND ART

A stand-alone printer is commonly used in conjunction with a computersystem in order to print images in the form of pictures, text, and/orgraphics that may be displayed on a monitor of the computer system. Avariety of technologies can be utilized by printers, including inkjettechnology and electrophotographic, or laser, technology.

A printing process using inkjet technology involves moving an inkjetcartridge horizontally along a vertically moving print medium, such as asheet of paper, and sequentially depositing ink by ejecting the ink ontothe paper to form an image. For color inkjet printing, the inkjetcartridge includes jets that are connected to four ink reservoirs. Thereservoirs contain cyan, magenta, yellow, or black ink. For grayscaleprinting, the inkjet cartridge typically includes a single reservoir ofblack ink.

A printing process using electrophotographic technology involvescreating neutral regions on a positively charged drum, which representsa reverse image of the image to be printed. The drum is then dusted withpositively charged particles, or toner. The toner is attracted to theneutral regions on the drum. When a negatively charged paper comes incontact with the drum, the attached toner transfers to the paper to formthe image on the paper.

Regardless of the technology utilized, a conventional stand-aloneprinter is typically fed with a print medium in which an image is to beprinted. The approach to feeding the print medium dictates the minimumsize of the printer. For example, in order to print onto a paper ofletter size, i.e. 21.59 cm×27.94 cm, a stand-alone printer must be atleast 21.59 cm wide to accommodate the letter-size paper. Since printmedia must be fed into a stand-alone printer, an image cannot be printedonto a rigid paper or other print media that cannot be fed into thestand-alone printer.

A solution to the minimum size requirement of a conventional stand-aloneprinter and the limited types of print media that can be used to printan image is a hand-held printer that can be manually manipulated over aprint medium. Because the print medium is not fed into the hand-heldprinter, the hand-held printer can be made much smaller than thestand-alone printers and can print on a greater variety of print media.U.S. Pat. No. 5,240,334 to Epstein et al. (hereinafter Epstein)describes a hand-held printer that is coupled to a host computer. Thehand-held printer described in Epstein is an inkjet printer that can beused to print addresses on envelopes. The hand-held printer is used inconjunction with a base unit that has grooves to guide the printerduring a printing process. The Epstein hand-held printer contains amechanical device with a ball that rolls on the print medium during theprinting process. The rotation of the ball is used to generate data fortracking the vertical and horizontal movement of the printer.

A concern with regard to the Epstein printer is that the ball used fortracking the printer may skid during the printing process. The effect ofsuch skidding is to generate incorrect data relating to the movement ofthe printer. Another concern with the use of the ball for tracking isthat the ball must be in constant contact with a print medium. If thehand-held printer of Epstein is temporarily removed from the printmedium during a printing process, the hand-held printer must be placedback on the print medium at the precise location where the printingceased in order to resume the printing process.

A similar inkjet hand-held printer is described in U.S. Pat. No.5,311,208 to Burger et al. (hereinafter Burger) that is also connectedto a host computer. The hand-held printer described in Burger includes acomputer mouse that is integrated into the housing of the hand-heldprinter. In one embodiment, a support unit is utilized to guide theprinter across a print medium in a horizontal direction. Similar to theprinter described in Epstein, the hand-held printer of Burger also usesa mechanical device with a ball to track the printer movement during theprinting process. The same concerns of Epstein are also present in thehand-held printer of Burger.

While the known hand-held printers operate well for their intendedpurpose, what is needed is an efficient hand-held printer with anon-mechanical tracking device.

SUMMARY OF THE INVENTION

A system and a method of printing an image represented by a frame ofimage data utilize a hand-held printer having at least one opticalsensor for tracking navigation of the hand-held printer relative to thesurface of a print medium. The change in position of the hand-heldprinter is monitored in real time using navigation information generatedby monitoring the outputs of the optical sensors. The tracking featureof the hand-held printer allows an operator to print an image onto aprint medium by moving the hand-held printer in a free-hand manneracross the print medium.

In the preferred embodiment, the hand-held printer includes four opticalsensors for tracking the position of the hand-held printer relative tothe print medium. However, fewer optical sensors may be utilized. Eachoptical sensor contains an array of optoelectronic elements to captureimages of the surface of a print medium at fixed time intervals.Preferably, the optical sensors detect slight pattern variations on theprint medium, such as paper fibers or illumination patterns formed byhighly reflective surface features and shadowed areas between raisedsurface features. These features can then be used as references fordetermining the movement of the hand-held printer. Alternatively, theoptical sensors can detect printed features on a print medium to be usedas references, such as graph paper lines or custom designs on thesurface of the print medium. By comparing images of the surface of aprint medium captured at different times, the movement of the hand-heldprinter can be determined. The navigation information generated by theoptical sensors is utilized to correlate the segment of the image to beprinted and the corresponding location of that segment on a printmedium.

In operation, a communication link is established between the hand-heldprinter and a host system. The host system can be a computer system. Inthe preferred embodiment, the communication link is a wirelessconnection, such that information is transmitted and received in theform of infrared or radio frequency signals. During a printing process,the hand-held printer is manually manipulated across a print medium. Thenavigation information generated by the optical sensors is relayed to aprocessor in the host system. The host system then transmits data thatrepresents the portion of the image to be printed at a particularposition on a print medium as the hand-held printer travels over thatparticular position. The data is sent in the form of print data to drivean inkjet cartridge to deposit droplets of ink. While inkjet printing ispreferred, other printing devices may be utilized.

In an alternative embodiment, the navigation information is processedwithin the hand-held printer. In addition, the image data to be printedis converted into print data by the hand-held printer. The conversion ofthe image data into print data is accomplished by a printer driver,which is typically implemented in computer software. The dynamicarrangement of segments of print data may be implemented at the driverlevel, or at a level above or below the driver level. That is, theprinter driver may direct print data in an arrangement of segmentsresponsive to the reception of navigation information. Alternatively,the dynamic arrangement of segments may be implemented prior to theprinter driver by arranging the image information that is seriallyconducted to the printer driver. As a third alternative, the print datafrom the printer driver may be temporarily stored in a buffer, and thedynamic arrangement may be the result of extracting print data from thebuffer in a sequence dictated by the navigation information.

By continuously monitoring the progress of the printing process, thehand-held printer is able to distinguish printed areas on the printmedium versus to-be printed areas on the print medium. The monitoringallows the hand-held printer to only print when the hand-held printer ison the to-be printed areas on the print medium.

An advantage of the invention is that since the tracking operation iselectrical rather than mechanical, tracking errors due to mechanicalfailures are eliminated.

Another advantage of the invention is that the optical tracking featureof the hand-held printer allows the operator to continue the printingprocess even though the hand-held printer is temporarily removed from aprint medium. The hand-held printer can use printed portions of theimage or other references on the print medium to determine the positionof the hand-held printer and to continue to print the remaining portionof the image.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an illustration of a hand-held printer that is connected to ahost computer system by a cable in accordance with one embodiment of thepresent invention.

FIG. 2 is a top view of the hand-held printer in accordance with thepresent invention.

FIG. 3 is a front view of the hand-held printer in accordance with thepresent invention.

FIG. 4 is a bottom view of the hand-held printer in accordance with thepresent invention.

FIG. 5 is a conceptual representation of generating navigationinformation using navigation sensors of the hand-held printer.

FIG. 6 is a block diagram of the components of the hand-held printer.

FIG. 7 is an illustration of a printing process using the hand-heldprinter in accordance with the present invention.

FIG. 8 is a flow diagram of a method of printing an image using thehand-held printer in accordance with the present invention.

DETAILED DESCRIPTION

In FIG. 1, a hand-held printer 10 embodying the present invention isshown connected to a host computer system 12 by a cable connection 14.The hand-held printer 10 has an appearance of a conventional computermouse. However, the appearance of the hand-held printer 10 can take on adifferent form without affecting the utility of the invention. The hostcomputer system 12 includes a monitor 16, a computer 18, and a keyboard20. Although the host computer system 12 is shown as a desktop computer,the host computer system 12 can be a laptop computer. The hand-heldprinter 10 is situated on a print medium 22. The print medium 22 can bean ordinary paper, a glossy paper, a cardboard, a file folder, a page ina notebook, a side of a box, or other similar medium that has a surfacefor an image to be printed. The print medium 22 could even be a sheet ofwood.

In another embodiment, the cable connection 14 is not needed. Instead, awireless connection is established between the host computer system 12and the hand-held printer 10. In this embodiment, the computer 18includes a transceiver (not shown) for transmitting and receiving datato and from the hand-held printer 10. The data can be transmitted in aform of infrared or radio frequency signals. In addition, the hand-heldprinter 10 includes a corresponding transceiver (not shown) forreceiving and transmitting data from and to the computer 18. The use ofthe transceivers eliminates the need for a physical connection betweenthe host computer system 12 and the hand-held printer 10.

The hand-held printer 10 functions as a conventional printer, althoughit is significantly more compact than a stand-alone printer. An image inthe form of a picture, text, and/or graphics is generated in ortransferred to the host computer system 12. The image can be displayedon the monitor 16 of the host computer system 12. Using a wordprocessor,photo-manipulation, or graphics software, the image displayed on themonitor 16 can be selected to be printed. In one embodiment, a frame ofimage data that represents a page of an image is converted within thecomputer 18 to print data in order to drive a printing mechanism in thehand-held printer 10. The print data is then sent to the hand-heldprinter 10 in a piecemeal fashion. In another embodiment, the entireframe of image data is transferred to the hand-held printer 10. Theconversion to print data is accomplished within the hand-held printer10. The printing operation of the hand-held printer 10 will be describedbelow.

Turning now to FIG. 2, a top view of the hand-held printer 10 is shown.A light indicator 24 is situated next to a print button 26 on theexterior of the hand-held printer 10. The light indicator 24 signals toa user when the conditions are such that a printing process can begin orcontinue. When an error occurs during the printing process, the lightindicator 24 can be designed to turn "off" as an error signal to theuser. Another situation in which the light indicator 24 can be designedto turn "off" is when the hand-held printer 10 is lifted from a printmedium during the printing process. The printing process is activated bythe print button 26. However, during the printing process, the actualprinting, i.e. depositing ink onto a print medium, occurs only when thehand-held printer 10 is manually maneuvered across the print medium withthe print button 26 activated. In other words, the actual printingoccurs only when the hand-held printer 10 is positioned on the printmedium, the print button 26 is activated, and the hand-held printer 10is moving. The circuitry associated with the print button 26 can beconfigured to require continuous depression by the user during theprinting process. Alternatively, the print button circuitry can bedesigned to be continuously activated when the print button 26 isdepressed once.

In FIG. 3, a front view of the hand-held printer 10 is illustrated. Thelight indicator 24 and the print button 26 that were described inreference to FIG. 2 are shown. On the bottom of the hand-held printer10, a portion of an inkjet cartridge 28 is situated between twonavigation sensors 30. Each navigation sensor 30 include a lens and anarray of optoelectronic elements. The size of the array ofoptoelectronic elements can vary, depending on the type ofoptoelectronic elements used and the desired area of a print medium tobe captured by the navigation sensors 30. The navigation sensors 30 areused to track movement of the hand-held printer 10 relative to a printmedium during a printing process. The inkjet cartridge 28 can be aconventional inkjet cartridge, such as the inkjet cartridges that areused in Hewlett Packard's line of Deskjet printers. However, the inkjetcartridge 28 can be specially designed to have a greater number ofinkjet orifices in order to print wider areas on a print medium as theinkjet cartridge 28 scans over the print medium. The inkjet cartridge 28can contain only black ink, for grayscale printing. Alternatively, theinkjet cartridge 28 can contain cyan, magenta, yellow, and black ink,for color printing.

Next to the navigation sensors 30 are two support spacers 32. Thesupport spacers 32 ensure that proper distance is maintained between theinkjet orifices of the inkjet cartridge 28 and a print medium during aprinting process when the hand-held printer 10 is positioned on theprint medium. In the preferred embodiment, the hand-held printer 10includes two additional navigation sensors and two additional supportspacers.

Turning to FIG. 4, a bottom view of the hand-held printer 10 is shown.Four navigation sensors 30 and four support spacers 32 are positionedaround the inkjet cartridge 28. The precise positions of the inkjetcartridge 28, the four navigation sensors 30, and the four supportspacers 32 are not critical to the invention. In addition, the number ofthe navigation sensors 30 and the number of support spacers 32 are notcritical to the invention. The hand-held printer 10 can operate wellwith only one navigation sensor 30. The support spacers 32 may bereplaced by bumps, or indentations, on the housing of the hand-heldprinter 10.

The navigation sensors 30 utilize a tracking process disclosed in U.S.Pat. No. 5,578,813 to Allen et al. (hereinafter Allen), which isassigned to the assignee of the present invention and is incorporated byreference. The Allen patent describes a scanning device forsimultaneously acquiring image and navigation information. A hand-heldscanning device is moved relative to a document having an image to becaptured. Simultaneously, one or more navigation sensors are used toview features on the scanned document and to generate navigationinformation. This same approach can be used in the printing process ofthe hand-held printer 10. In a sophisticated application of thisapproach, the features that are imaged and used to determine positioninformation may be paper fibers or illumination patterns formed byhighly reflective surface features and shadowed areas between raisedsurface features. In a less sophisticated application, the features thatare imaged may be reference features, such as graph paper lines on thesurface to which the image is to be printed.

FIG. 5 is a conceptual representation of generating navigationinformation using the navigation sensors 30 of the hand-held printer 10.A reference frame 62 of a surface on which an image is to be printed isshown as having a T-shaped feature 64. The size of the reference framedepends upon factors such as the maximum scanning speed of the hand-heldprinter 10, the dominant spatial frequencies of the image of thestructural features, and the image resolution of the navigation sensors30. A practical size of the reference frame for a navigation sensor 30that is thirty-two pixels by sixty-four pixels is 24×56 pixels.

At a later time (Δt), the navigation sensor 30 acquires a sample frame66 of the surface on which the image is being printed. The sample frame66 is acquired after the hand-held printer 10 has been displaced withrespect to the position in which frame 62 was acquired. The duration Δtis preferably set such that the relative displacement of the T-shapedfeature 64 is in the range from about 0.5 pixel to about 1.5 pixel ofthe navigation sensor at the velocity of translation of the scanningdevice. However, durations outside this range may be used. An acceptableduration is 50 μs for velocities of 0.45 meters/sec at 600 dpi.

If the hand-held printer 10 has moved during the time period betweenacquiring the reference frame 62 and the time at which the sample frame66 is acquired, the first and second images of the T-shaped feature willbe ones in which the feature has shifted. While the preferred embodimentis one in which Δt is less than the time that allows a full-pixelmovement, the schematic representation of FIG. 5 shows the feature 64 ashaving shifted upwardly and to the right by one full pixel. Thefull-pixel shift is assumed only to simplify the representation.

Element 70 in FIG. 5 represents a sequential shifting of the pixelvalues of frame 68 into the eight nearest-neighbor pixels. That is, step"0" does not include a shift, step "1" is a diagonal shift upward and tothe left, step "2" is an upward shift, etc. In this manner, thepixel-shifted frames can be combined with the sample frame 66 to producethe array 72 of position frames shown in FIG. 5. The position framedesignated as "Position 0" does not include a shift, so that the resultis merely a combination of frames 66 and 68. "Position 3" has theminimum number of shaded pixels and, therefore, is the frame with thehighest correlation. Based upon the correlation results, the position ofthe T-shaped feature 64 in the sample frame 66 is determined to be adiagonal rightward and upward shift relative to the position of the samefeature in the earlier-acquired reference frame 62, which implies thatthe hand-held printer 10 has moved leftwardly and downwardly during thetime Δt.

In FIG. 6, a block diagram of the components of the hand-held printer 10is illustrated. An interface 74 is connected to a processor 76. Theinterface 74 can be a connector for a cable to establish a communicationlink between the hand-held printer 10 and the host computer system 12.In an alternative embodiment, the interface 74 is a transceiver. In thisembodiment, infrared or radio frequency signals are utilized tocommunicate between the hand-held printer 10 and the host computersystem 12. The processor 76 is also connected to the navigation sensor30 and the inkjet cartridge 28. Although only a single navigation sensor30 is shown, the hand-held printer 10 can embody additional navigationsensors. In the preferred embodiment, the hand-held printer 10 has fournavigation sensors. Similarly, additional inkjet cartridges can beutilized. However, due to the relatively large size of an inkjetcartridge, a single inkjet cartridge having a large area for ejectingink is preferred.

Also connected to the processor 76 is memory 78 and a power source 80.The power source 80 may be a battery to supply power to the electroniccomponents of the hand-held printer 10. The battery may be arechargeable nickel-cadmium battery or a conventional alkaline battery.The need for the power supply 80 can be eliminated if a cable is used toestablish the communication link between the hand-held printer 10 andthe host computer system 12. A supply of power can be transferred fromthe host computer system 12 to the hand-held printer 10 through thecable.

The memory 78 may be a conventional dynamic random access memory device.The storage capacity of the memory 78 can vary depending on the numberof optical sensors utilized by the hand-held printer 10. The capacity ofthe memory 78 is not crucial to the invention. The memory 78 may storeprinter driver software pre-programmed to drive the inkjet cartridge 28.In another embodiment, the memory 78 is coupled to read-only memory (notshown) that is programmed with the printer driver software.

In an alternative embodiment, the hand-held printer 10 does not containthe processor 76 and the memory 78. The functions of the processor 76and the memory 78 are performed by the host computer system 12. However,the printing operation of the hand-held printer 10 in this embodimentfunctions in the same manner as described below.

The operation of the hand-held printer 10 will be described withreference to FIGS. 1, 4, 5, 6, and 7. First, an image in the form of apicture, text, and/or graphics is displayed on the monitor 16 of thehost computer system 12 using wordprocessor, photo-manipulation, orgraphics software. If the displayed image is to be printed, a userinitiates the printing process by inputting the required print commandinto the computer 18 through print button 26 on the printer 10, thekeyboard 20 or a computer mouse (not shown). A frame of image data,representing the displayed image in digital form, is transmitted to thehand-held printer 10. In one embodiment, the frame of image data istransferred to the hand-held printer 10 through the cable connection 14.In another embodiment, the frame of image data is transferred to thehand-held printer 10 as infrared or radio frequency signals.

The frame of image data is received by the interface 74 and relayed intothe memory 78 in the hand-held printer 10. Meanwhile, the user placesthe hand-held printer 10 on a print medium such as a sheet of paper.Preferably, the hand-held printer 10 is placed on a designated startingposition on the paper. If the hand-held printer 10 is programmed, as adefault, to begin printing the upper left corner of the image, thestarting position is where the user desires the upper left corner of theimage to be printed. Other locations of the image can be programmed tobe printed first. The light indicator 24 on the hand-held printer 10turns "on" at this time to signal that the hand-held printer 10 is readyto print. The user then activates the print button 26 and begins tomanually maneuver the hand-held printer 10 across the paper, scanningthe area of the paper in which the image is to be printed. In analternative method, the hand-held printer 10 is scanned to find a cornerof the paper, for example, the top left corner. The corner will be usedas a reference for printing the image onto the paper. In thisembodiment, the light indicator 24 will not turn "on" until thehand-held printer 10 determines the position of the inkjet orificesrelative to the corner.

When the hand-held printer 10 is moved during the printing process, thenavigation sensors 30 determine the relative movement of the hand-heldprinter 10 with respect to the paper. Using the approach described abovein reference to FIG. 5, the navigation sensors 30 capture new frames ofreference data that are compared with captured frames by the processor76 to monitor the movement of the hand-held printer 10. The frame ofimage data to be printed is converted by the processor 76 into printdata. The processor 76 sends to the inkjet cartridge 28 that portion ofthe print data representing the portion of the image that needs to beprinted, as determined at each cycle (Δt) in which the hand-held printer10 has been moved. The conversion of the image data into print data isaccomplished by a printer driver (not shown), which is typicallyimplemented in computer software. The dynamic arrangement of segments ofprint data to correspond to the dynamic movement of the printer 10 maybe implemented at the driver level, or at a level above or below thedriver level. That is, the printer driver may direct print data in anarrangement of segments responsive to the reception of navigationinformation. Alternatively, the dynamic arrangement of segments may beimplemented prior to the printer driver by arranging the imageinformation that is conducted to the printer driver. As a thirdalternative, the print data from the printer driver may be temporarilystored in a buffer, and the dynamic arrangement may be the result ofextracting print data from the buffer in an arrangement dictated by thenavigation information.

Depending on the new position of the hand-held printer 10, the processor76 sends corresponding print data to the inkjet cartridge 28. In thismanner, the whole image is printed when the hand-held printer 10 hasscanned the entire area of the paper in which the image is to beprinted. During the printing process, the hand-held printer 10 can beconfigured to update the host computer system 12 by transmittinginformation concerning the printed areas versus the areas yet to beprinted. This information can be used by the host computer system 12 tohighlight the portion of the printed image in the displayed image on themonitor, allowing the user to determine the progress of the printingprocess. This information is also utilized by the hand-held printer 10to ensure that the hand-held printer 10 will not reprint over a printedarea when the hand-held printer 10 is positioned over the printed area.

In many instances, the hand-held printer 10 will scan an area previouslyprinted or missed portion of the paper. As described above, thehand-held printer 10 will not print over a printed area. In a similarmanner, when the hand-held printer 10 is scanned over the missed area,the hand-held printer 10 will print the corresponding portion of theimage to be printed onto the missed area.

In FIG. 7, an illustration of the printing process is shown. An image ofthree mountain peaks is visible in FIG. 7. The solid lines of themountains represent the printed portion of the image, while the dottedlines represent the portion of the image that needs to be printed.Swaths 82, 84, and 86 illustrates the path of the inkjet orifices of thehand-held printer 10 over a print medium. The hand-held printer 10 hastraveled from point A to point B. The swath 82 represents a left toright path of the hand-held printer 10. During the passage of thehand-held printer 10 over the swath 82, the portion of the image withinthe swath 82 was printed. The swath 84 represents a right to left pathof the hand-held printer. The upper portion of the swath 84 overlaps thebottom of the swath 82. As described above, the hand-held printer 10does not print over a printed portion of a print medium. The overlap ofthe swaths 82 and 84 ensures that there are no missed areas on the printmedium between the swaths 82 and 84. The swath 86 represents anotherleft to right path of the hand-held printer 10. However, the swath 86does not overlap a lengthwise edge of the swath 84. The result is that aportion of the print medium has been missed by the printer. As indicatedby the dotted lines of the mountains between the swaths 84 and 86, thearea between the swaths 84 and 86 needs to be printed. In order to printthe missed portion of the print medium, the user need only to scan overthe missed area with the hand-held printer 10.

Assuming the hand-held printer 10 was lifted away from the print mediumat point B, the user can print the missed portion by placing thehand-held printer 10 back onto the print medium at any point where thehand-held printer 10 had previously scanned. The hand-held printer 10can use stored images of pattern variations of the print medium or theprinted portion of the image as references to reinitiate the printingprocess. The preferred method is to scan an area covered previouslyduring the printing process. The light indicator 24 will turn "on" whenthe hand-held printer 10 has determined the relative position. Then, theprinting process can resume. Although only horizontal paths areillustrated in FIG. 7, the hand-held printer 10 is not limited tohorizontal printing paths. The direction of the hand-held printer 10does not affect the printing process. The hand-held printer 10 can bemanually manipulated in horizontal, vertical, diagonal, or even circularmotions. The only requirement to print a complete image is that theentire area of the print medium, where the image is to be printed, mustbe scanned by the hand-held printer.

The hand-held printer 10 can also be used with various pre-printedpapers having custom designs, such as forms or personalized letterpaper. The designs can be loaded as design image data into the hand-heldprinter 10 by a storage disk, or can be scanned into the hand-heldprinter 10 using the navigation sensors 30. The designs can then be usedas reference points during a printing process.

FIG. 8 shows a flow diagram illustrating a method of printing an imageusing the hand-held printer 10 in accordance with the present invention.At step 110, a communication link is established between a host systemand the hand-held printer 10. The host system is preferably a computersystem such as a desktop computer or a laptop computer. In oneembodiment, the communication link is established through a cable thatphysically connects the hand-held printer 10 with the host system. Inanother embodiment, the communication link is established though awireless connection. In the wireless connection embodiment, infrared orradio frequency signals are utilized to transmit and receive databetween the hand-held printer 10 and the host system.

In step 120, a frame of image data that represents the image to beprinted is transmitted from the host system to the hand-held printer 10through the communication link. At step 130, the hand-held printer 10 ismanually manipulated across a print medium in order to print. Thehand-held printer 10 is initially placed on a designated position on theprint medium. While the hand-held printer 10 is manually manipulated,the hand-held printer 10 tracks positions of the hand-held printer 10relative to the surface of the print medium and generates position datathat indicates the relative position at step 140. The tracking ofpositions is accomplished by comparing surface images of the printmedium captured by the navigation sensors in the hand-held printer 10.The comparison of the surface images may involve comparing images offibers on the print medium or other pattern variations on the printmedium. When the hand-held printer 10 is manipulated over a portion ofthe print medium in which the image is be printed, the hand-held printer10 deposits print-forming material onto the surface of the print mediumat step 150. The determination by the hand-held printer 10 to depositprint-forming material over a particular portion on the print mediuminvolves correlating the position data with the frame of image data suchthat a section of the image can be printed on the corresponding locationon the print medium.

What is claimed is:
 1. A hand-held printing system for printing an imageonto a print medium comprising:a printer housing; interface meansaffixed to said printer housing for receiving data representative ofsaid image to be printed; optical means affixed to said printer housingfor forming navigation information that is responsive to opticallyimaged surface variations during non-linear navigation of said printerhousing along said print medium, thereby generating non-linearnavigation information, said optical means having an output indicativeof two-dimensional positions of said printer housing relative to saidprint medium; a supply of print-forming material; and print means fordepositing said print-forming material onto said print medium in asequence that is responsive to said non-linear navigation informationand in an image pattern that is responsive to said data.
 2. The systemof claim 1 further comprising a navigation processor operativelyassociated with said optical means to monitor non-linear movement ofsaid printer housing relative to said print medium.
 3. The system ofclaim 2 wherein said print means includes printer driver software forconverting said data to print data having a data arrangement determinedby said non-linear navigation information.
 4. The system of claim 1wherein said optical means includes an optical sensor having an array ofoptoelectronic elements.
 5. The system of claim 1 wherein said printmeans includes an inkjet cartridge and said supply of print-formingsubstance is ink within said inkjet cartridge.
 6. The system of claim 1wherein said interface means includes a transceiver that is capable oftransmitting and receiving said data in either infrared or radiofrequency signals.
 7. The system of claim 1 wherein said interface meansincludes a cable for establishing a communication link to an externaldevice.
 8. The system of claim 1 wherein said interface means includesan input in communication with a host computer.
 9. A printing systemcomprising:a printer housing; an input/output port attached to saidprinter housing for establishing a connection with an external device; aprinting mechanism contained within said printer housing, said printingmechanism having a print-forming region at an exterior surface of saidprinter housing to form an image onto an external surface in response toa two-dimensional movement of said printing mechanism with respect tosaid external surface; and an optical sensor having an array ofoptoelectronic elements located on said printer housing for monitoringpattern variations on said external surface, said optical sensorgenerating navigation information indicative of non-linear navigation ofsaid print-forming region with respect to said external surface on whichsaid image is to be printed, said optical sensor being operativelyassociated with said printing mechanism such that said printingmechanism is responsive to said navigation information and such thatprinting onto said external surface is in a sequence that is determinedby said non-linear navigation information.
 10. The system of claim 9further comprising a navigation processor located within said printerhousing, said navigation processor being operatively connected to saidoptical sensor, said navigation processor receiving said navigationinformation from said optical sensor during said non-linear navigationto ascertain changes in said relative position of said print-formingregion with respect to said external surface.
 11. The system of claim 10further comprising memory located within said printer housing forstoring said navigation information and image data received from saidexternal device, said memory being coupled to said navigation processor.12. The system of claim 11 further comprising a printer driveroperatively associated with said memory and said processor to convertsaid image data into print data, said print data being transmitted tosaid printing mechanism.
 13. The system of claim 9 wherein said printingmechanism includes an inkjet cartridge and a supply of ink within saidinkjet cartridge.
 14. The system of claim 9 wherein said input/outputport includes a transceiver that is enabled for transmitting andreceiving said data in either infrared or radio frequency signals.
 15. Amethod of printing an image represented by a frame of image data using ahand-held printer having an optical sensor comprising steps of:manuallymoving said hand-held printer adjacent to a surface on which a printedimage is to be formed in a non-linear manner; tracking two-dimensionalpositions of said hand-held printer relative to said surface bymonitoring pattern variations on said surface using said optical sensor,including generating two-dimensional position data indicative of saidtwo-dimensional positions; and depositing print-forming material ontosaid surface in a sequence determined by said two-dimensional positiondata such that a composite printed image is representative of said imagedata, including correlating said two-dimensional position data with saidimage data.
 16. The method of claim 15 further comprising a step ofreceiving said frame of image data by said hand-held printer andgenerating print data within said hand-held printer to drive a printingmechanism of said hand-held printer in response to said frame of imagedata.
 17. The method of claim 15 further comprising a step ofestablishing an infrared or a radio frequency communication link with ahost system.
 18. The method of claim 15 wherein said step of depositingsaid print-forming material includes utilizing inkjet printingtechniques.
 19. The method of claim 15 further comprising steps ofremoving said hand-held printer from said surface after said step ofdepositing said print-forming material onto said surface and thenreinitiating said step of depositing said print-forming material ontosaid surface.